Calculate values in same field

[ekariuki]

Hallo,

I have a table Routes that contains a route name and when the route runs. I would like to calculate the difference between the last run Day and the one after it. This will populate in the RunDateDiff field.

My table: Tbl_Route

RouteName RunDate Stop RunDateDiff
A 12/1/2009 Clinton
A 12/3/2009 Townsent
A 12/3/2009 Nowhere
A 12/10/2009 Somewhere

Results I am looking for:

RouteName RunDate Stop RunDateDiff
A 12/1/2009 Clinton 0
A 12/3/2009 Townsent 2
A 12/3/2009 Nowhere 2
A 12/10/2009 Somewhere 9

Thank you for your help.

[ChipR]

the last run Day and the one after it

Your rules are not clear. What do you mean by this?
12/3/09 - 12/1/09 = 2, but where does the 9 come from?